Coatings for optical fibers which offer protection against moisture and high temperature as well as resistance against salt water, harsh chemical environments, such as acidic or basic, while providing coating continuity and resistance to cracking and crack propagation are difficult to achieve.
The prior art has focused around organic coatings such as ultraviolet (UV) acrylates and Chemical Vapor Deposition (CVD) of, for example, TiC. In the case of acrylates, these coatings are not stable at temperatures above 200.degree. C. and their hermaticity is low to nonexisting even at room temperatures. Application of ceramic coatings using chemical vapor deposition (CVD) are very limited in their chemical composition. Usually these coatings are simple ceramics such as TiC, SiO.sub.2, and Si.sub.3 N.sub.4, for example. Application of multi-function compounds is at best difficult and must be performed in more than one step. In other words, if a Si.sub.3 N.sub.4 -SiO.sub.2 -TiC coating is desired, three distinct steps are required and three distinct CVD systems must be utilized. These multifunction applications are thus very expensive and complex.